I read that as
(4a^2-1)/(4a^2-16) * (2-a)/(2a-1) , my brackets are necessary
= (2a+1)(2a-1)/( 4(a+2)(a-2) * (2-a)/(2a-1)
the (2-a)/(a-2) are opposite, they will give you the -1
so..
= -(2a+1)/(4(a+2)) , again you have to use brackets to write it on here.

Thanks Reiny =) But I to get everything clear, the 2-a and the a-2 cancel right? After I cancel those I am left with (2a+1) as the numerator:S Sorry I am just confused. Also did you factor out the 2a+4 and 2a-4 to get 4(a+2)(a-2)? Could you please explain step by step?